The Wilvos founder said Trinder was dehydrated and starving when rescued and although it was not known how long his mother had been dead, he had probably not been getting the nourishment he needed for some time.

Trinder was taken to the Australia Zoo Wildlife Hospital on January 14 where he was rehydrated and had plumped up to 60g by the time he came in to Mrs Whiting's care three days later.

Thanks to six feeds a day of marsupial formula and fluids in between for the last six weeks, he now weighs a much healthier 100g or so and is growing fur but is still underweight for his age.

"He should be 130g because he's got fur coming," Mrs Whiting said.

She said getting him to feed was initially difficult but was now easier.

"When he came in, he was pretty terrible. I had a really tiny thin tube that I got him to suck off but this week, I'm getting him to lap," she said.

Sylvia Whiting with another brushtail possum in care.Patrick Woods

Mrs Whiting expects Trinder to continue to make progress and to be ready for release in a few months but said he would always be blighted by this past summer.

"They have to get to 1300-1400g to be released. I don't think he'll grow as big as the other possums would. I expect he'll always be stunted."

Mrs Whiting is also caring for an underweight juvenile rosella parrot.

She said the dry weather not only meant animals went without water but also reduced their food sources.

"There's not as much nectar in the trees. If there's no nectar, there's no insects coming, so the insectivorous and the nectar-feeders suffer," she said.

Wilvo Sylvia Whiting encourages people to leave some water out for wildlife.Patrick Woods

Mrs Whiting said a creek at her property had run dry for the first time in 40 years and this week's rain had done little but turn it into sludge.

She said without a rain and a flush of growth before the cool weather set in, it would be a tough winter for wild animals which were already underweight.

She urged householders to leave water containers out to help the wildlife, at heights for birds as well as ground level for other animals.

She said ground level water containers should be refilled every morning with fresh water because cane toads liked to bask in them at night.